Knife sharpener

ABSTRACT

An apparatus for automatically sharpening microtome knives which repetitively strokes alternate sides of a microtome knife in a straight line motion against a planar non-stationary honing plate. The honing surface of the honing plate moves in a circular path within the principal plane of the plate. The honing surface of the honing plate is selectively positioned in a one of a plurality of parallel planes so that the knife edge is ground at a selected one of a corresponding plurality of angles. In a similar second mode of operation, a substantial pressure may be selectively applied to the knife against the honing plate to provide a high-speed sharpening operation. In a third mode of operation two worn honing plates are automatically resurfaced using a removable attachment to maintain a second honing plate in a stationary position supported by a moving abrasive-coated first honing plate. In this mode, the knife stroking means is stationary.

States Guerra et a1.

atet [1 1 KNIFE SHARPENER [75] Inventors: John P. Guerra, Buffalo; Chester S.

Ingraham, East Aurora, both of 7 NY. [73] Assignee: American Optical Corporation,

Southbridge, Mass.

[22] Filed: Dec. 18, 1972 [21] Appl. No.: 316,317

[52] US. Cl. 51/58, 51/109 BS, 51/122 [51] Int. Cl B24b 7/02, B24b 3/48 [58] Field of Search 51/57, 58, 119, 64, 68, 51/69, 120, 122, 157-159, 153

[56] References Cited UNITED STATES PATENTS 1,001,735 8/1911 Denison 51/159 X 1,091,939 3/1914 Lo Casto 51/159 1,166,843 1/1916 Loesser 51/229 X 1,427,130 8/1922 Strand 51/159 2,834,160 5/1958 Lillie 51/165 R 3,107,457 10/1963 Walters 51/119 X 3,145,509 8/1964 Heesemann 51/141 3,266,198 8/1966 Schramko 51/158 Primary Examiner-Al Lawrence Smith Assistant ExaminerMarc R. Davidson Attorney, Agent, or FirmAlan H. Spencer; William C. Nealon [5 7 ABSTRACT An apparatus for automatically sharpening microtome knives which repetitively strokes alternate sides of a microtome knife in a straight line motion against a planar non-stationary honing plate. The honing surface of the honing plate moves in a circular path within the principal plane of the plate. The honing surface of the honing plate is selectively positioned in a one of a plurality of parallel planes so that the knife edge is ground at a selected one ofa corresponding plurality of angles. In a similar second mode of operation, a substantial pressure may be selectively applied to the knife against the honing plate to provide a highspeed sharpening operation. In a third mode of operation two worn honing plates are automatically resurfaced using a removable attachment to maintain a sec- 0nd honing plate in a stationary position supported by a moving abrasive-coated first honing plate. In this mode, the knife stroking means is stationary.

5 Claims, 5 Drawing lFigures PAIENTEBnms I974 3844367 SHE EY 20? 5 FIG. 2

PATENTEUnmzsmm 3.844L067 sum 50? s KNIFE SHARPENER BACKGROUND OF THE INVENTION This invention relates to automatic tool sharpening sharpening microtome knives.

It is well known in modern medical laboratories that cutting knives require a uniformly sharp and even edge in order to be useful in the preparation of tissue sections using microtomy techniques. In the prior art, methods of microtome knife sharpening, such as taught by U.S. Pat. No. 3,041,790, use a rapidly rotating sharpening wheel in conjunction with an abrasive suspension coating. Such an apparatus has substantial limitations in the evenness and sharpness of the knife edges produced.

It is well known that an improved knife sharpening apparatus is provided by an automatic knife sharpener for microtome knives in which alternate sides of a microtome knife are automatically slowly-stroked in a straight line against a stationary abrasive-coated planar glass honing plate. An example of an apparatus for performing such an automatic operation is the Automatic Microtome knife Sharpener, Model 935 manufactured by the assignee of the present invention. This apparatus, however, is subject to substantial practical limitations for use in modern medical laboratories. A first such limitation is the substantial length of time required to produce a sharpened microtome knife. In that apparatus, a nicked or dull knife requires many hours of sharpening to produce a satisfactory cutting edge. A second disadvantage of this previous apparatus is related to the wear on the glass honing plate. As the knife being sharpened is stroked repetitively across the stationary honing plate, substantial wear in the honing surface of the plate takes place at the points of contact with the knife, requiring frequent replacement of the honing plates. Due to the expense of replacing such worn honing plates, it is the general practice to lap two such worn plates together by hand or by a special lapping machine or a device adapted for that purpose. The expense of providing the necessary hand labor or the additional lapping machine to recondition the honing plates is substantial, although less than the cost of directly replacing the plates. A further disadvantage of the previous apparatus for automatic knife sharpening relates to the abrasive suspension coating which is applied to the honing plate. In the previous apparatus, the honing plate vibrates at a rate to distribute the abrasive particles within thesuspension coating. However, the constant back-and-forth stroking of the microtome knife offsets to a large extent the effect of this vibration and tends to collect the abrasive coating at certain cations and remove the coating from other locations. As a result, constant reapplication of an abrasive suspension coating is required to prevent non-uniform sharpening of the microtome knife. Thus, the automatic microtome knife sharpener of the prior art may provide an adequately sharpened microtome knife; however, the apparatus is both expensive and inconvenient to use in the environment of a modern medical laboratory.

. SUMMARY OF THE INVENTION The foregoing problems associated with prior art knife sharpeners are significantly reduced by the microtome knife sharpener of the present invention which includes selective pressure meanstranslatable to the knife to be sharpened, a laterally translating honing plate support means and a removable honing plate lapping means.

Accordingly, it is one of the objects of this invention to provide a new and improved apparatus for the automatic sharpening of microtome knives.

Another object is to provide a new and improved apparatus for rapidly resharpening a microtome knife.

A further object is to provide a new and improved apparatus for sharpening microtome knives against a laterally translating glass honing plate, which has a long sharpening lifetime.

Still a further object is to provide a new and improved automatic microtome knife sharpening apparatus having a removable attachment for resurfacing worn glass honing plates.

Still another object is to provide a new and improved automatic microtome knife sharpening apparatus having an abrasive suspension coating which remains uniformly distributed on the sharpening surface for a substantial period.

The foregoing and other objects of this invention, the various features thereof, as well as the invention itself may be more fully understood from the following description when read together with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates a top view of an automatic microtome knife sharpener in accordance with the invention;

FIG. 2 illustrates a side view of an automatic microtome knife sharpener in accordance with the invention;

FIG. 3 is an isometric view of the solenoid activated pressure generating assembly of the sharpener in FIG.

FIG. 4 is an isometric view of the honing plate. translating and support assembly of the embodiment shown in FIG. 1; and

FIG. 5 is an isometric view of the honing plate resurfacing attachment in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS At the outset, the process of the present invention is described in its broadest overall aspects with a more detailed description following.

In the present invention, an automatic microtome knife sharpener is provided with a stroking means for alternately stroking in a straight line, a first and second side of a microtome knife against an abrasive-coated planar glass honing plate. The knife being sharpened is positioned by the stroking means at a predetermined angle to the honing plate. In a sharpening mode of operation, the honing plate is laterally translated in a circular path, that path lying within the principal plane of the plate. The honing plate is also selectively positioned so that'the honing surface lies within one of a plurality of parallel planes, so that the knife which is positioned by the stroking means is at a corresponding one of a plurality of predetermined angles with respect to the plane of the honing surface. Thus, the knife being sharpened is stroked on alternate sides in aback-and forth motion across the circularly translating honing plate. During this sharpening mode of operation, the

. precise angle of the cutting edge with respect to the transverse plane of symmetry of the knife is determined by the angular position of the knife with respect to the stroking means in conjunction with the position of the honing surface of the glass plate.

In addition, a solenoid activated pressure means may selectively apply via mechanical linkage, including a scissors spring, a substantial torque to the stroking means, which in turn applies a substantial pressure to the knife against the honing plate. The scissors spring provides that a controlled force is applied to the stroking means and ensures that the solenoid is not overloaded. When the solenoid pressure means is activated, the generated pressure on the knife against the honing plate produces a rapid wearing of the knife at the points of contact with the honing plate so as to produce a rapid grinding of the cutting edge of the knife. The rapid grinding is enhanced when used with a coarse abrasive suspension on the honing plate to provide a so-called coarse sharpening operation.

A second facet on the cutting edge of the knife is ground in a so-called FINE honing mode in which the solenoid activated pressure means is stationary with the knife removed from the plate and the position of the honing plate is such that the transverse plane of the knife is at a larger angle with respect-to the honing plate than during the COARSE honing mode of operation. In addition, during the FINE honing action, a fine abrasive suspension is used on the honing plate. In this manner, the present invention is used to provide a rapid coarse sharpening of a microtome knife to remove large nicks and scratches followed by a slower fine sharpening to produce a smooth, uniform and substantially scratch-free, two facet per side cutting edge.

During both the COARSE and FINE sharpening modes, the glass honing plate is laterally translated in a circular path lying in the plane of the plate. The circular motion of the honing plate provides for rapid sharpening and long wear of the honing plate by ensuring that the points of contact of the knife on the honing plate are distributed over a larger surface than in prior automatic sharpencrs. in addition, the circular motion ofthe honing plate is effective to distribute the abrasive coating used in the honing action so that continuous monitoring and replacement of the coating is not required. In this manner, as much as a 50 percent saving in time required to sharpen a microtome knife may be achieved with the present invention as compared with prior automatic knife sharpencrs.

In a third LAP mode of operation. two worn honing plates may be automatically resurfaced. In this mode, a first worn honing plate is translated in a circular motion as in the previously described COARSE and FINE modes of operation. A removable attachment is provided to maintain a second worn honing plate in a stationary position and supported by the circularly translating first honing plate. In this mode of operation, the stroking means is stationary. With an appropriate abrasive placed between the two honing plates, the relative motion of the plates is used to lap the adjacent surfaces of the two plates. The lapping action provides a uniformly smooth surface on the honing plates which may be worn from prior knife sharpening operations. In this manner a single apparatus may be used to both sharpen microtome knives and to maintain or resurface honing plates used during the sharpening process.

The knife sharpener ofthe present invention is shown in H65. 1 and 2. In FIG. 1, knife sharpener 10 includes a microtome knife 12 to be sharpened which is held in an upraised position by a clamp assembly 14 and arm 16 of stroking assembly 20. in FIG. 2, knife 12 is held by clamp 14 against a honing plate 41 in an appropriate position for sharpening. Stroking assembly 20 is positioned to reciprocate in a horizontal plane. A planar glass honing plate 41 is shown in a translating honing plate support 42. Front panel control switches 43-48 provide controls for selecting the operational mode of sharpener 10.

The present invention includes a stroking assembly of the form substantially similar to that used in the Automatic Microtome Knife Sharpener, Model 935, manufactured by the assignee of this invention, that assembly not being a part of this invention. Stroking assembly 20 includes a motor driven assembly which is gear driven repetitively in a four segment cycle to move continuously backward and forward (forward being defined as toward front panel along lubricated slide rods 22 and 23. Assembly 20 may operate at a slow rate, for example, one backward and forward excursion every four seconds.

Arm 16 of stroking assembly 20 includes a knife clamp 14 which has thumb-screw actuated clamps 14a and 14b for holding a microtome knife 12 at a predetermined angle with respect to arm 16. Arm 16 is also mechanically connected to pivot about a horizontal axis 25 at points 25a and 25b of assembly 20. Arm [6 is further connected to lever arms 27 and 28. Appropriate forces, as described hereinbelow, may be effective when applied to a one of lever arms 27 or 28 to apply torques about axis 25 on the arm assembly 16, which torques respectively are effective to either flip knife 12 or force knife 12 against plate 41. Component parts 33-35 and cam actuated arm 36 comprise the knife flipping assembly portion of assembly 20. In operation, stroking assembly 20 is effective to cyclicly translate four times in a backward and forward direction along slide rods 22 and 23. During the first three segments of a cycle, arm 16 positions knife 12 such that an edge is in contact with plate 41. During every fourth cycle, arm 36 is cam actuated from the drive motor of assembly 20 to be in an obstructing position so as to strike lever arm 27 during the backward motion of assembly 20. The resultant force applied to lever arm 27 as assembly 20 moves along slide rods 22 and 23 is effective to rotate arm 16 about axis 25 in such a manner that knife 12 is raised from a normal position in contact with honing plate 41 to a position above that plate. During the backward motion of assembly 20 along slide rods 22 and 23, arm 16 is rotated 90 by the action of cams 33 and 35 against plate 34. During the subsequent forward motion along slide rods 22 and 23, arm 36 remains in its obstructing location, but the forward motion of assembly 20 allows arm 16 to gradually lower knife 12. Also during this forward motion of assembly 20, cams 33 and 35, together with plate 34, are effective to rotate arm 16 an additional 90. At the termination of this fourth cycle of backward and forward motion of assembly 20, knife 12 is positioned again in contact with plate 41 by arm 16 and clamp 14. Thus, during the lifting and lowering of arm 16 as described above, parts 33-35 are effective to act as a flipping assembly and are effective to rotate the knife clamp assembly 14, together with knife 12, about the axis of arm 16. In summary,

stroking assembly 20 is effective to repetitively translate along slide rods 22and'23 for'three full backward and forward segments while maintaining a first side of knife 12 in contact with honing plate 41. During a fourth backward and forward segment, knife 12 is raised and flipped over before returning again to contact with plate 41. The above described operation of stroking assembly 20 is substantially similar to that used in the Automatic Microtome Knife Sharpener, Model 935, and is not a part of this invention.

In the present invention, an improvement in the knife sharpening operation of sharpener is achieved by the addition of a solenoid actuated pressure generating assembly 50 which is in detail in FIG. 3. Assembly 50 is effective to selectively apply a force to lever arm 28 of stroking assembly in such a manner so that the resultant torque tends to rotate arm 16 and knife 12 about axis in a downward'direction during the stroking portion of the above described cycle of operation.

The applied torque results in an increased force, for example, .4 pounds, which is applied to knife 12 against honing plate 41. During operation when solenoid assembly 50 is not activated, then the sole means of pressure applied to knife 12 against plate 41 is the gravitational force resultant from the mass of the knife clamp assembly 14 and the knife 12 itself.

In FIG. 3, assembly 50 is shown to include mounting bracket 51 which is attached to assembly 20 and moves along slides 22 and 23 with that assembly. Bracket 51 is used to support solenoid 53. Solenoid movable core 53a is connected by links 55 and 56, scissors spring 63 and link 57 to cam 58..Li'nks 56 and 57 are attached via screw 61 to supportplate 51 in a manner permitting those lengths to pivot about screw 61 Scissors spring 63 is also mounted on screw 61, having extensions 63a and 63b. In addition screw 61 has a spacing bushing and a flexible bushing to allow play inthe motion of cam 58. Extensions 63a and 63b of spring 63 are positioned adjacent to tabs 56a and 57a of respective links 56 and 57. Cam 58 includes cavity 580 which extends a substantial distance into cam 58 from the side of that cam away from plate 51. Cam 58 further includes screw 58b which extends from the side of cam 58 adjacent to plate 51. Screw 58b extends through a horizontal slot in plate 51 and guides the motion of cam 58. The-function of cavity 58a is described below.

The broadest portion of cam 58 is positioned so as to lie within a cutout area 67 of panel 51 when solenoid 53 is not energized. A scissors spring 68 is attached via a first extension of that spring to the portion of screw 58b which extends through panel cutaway 67 of plate 51. Spring 68 is mounted on a supporting stud 69 attached to plate 51 with the second extension of the spring 68 anchored in hole71of support 51. Spring 68 is effective to position cam 58 so that the broad portion of that cam lies within the cutout 67 as such times as when the solenoid 53 is not energized. When solenoid 53 is energized, cam 58 is moved toward that solenoid as permitted by screw 58b in the slot of plate 51 in such a manner as to position cavity 58a at an increased distance from support 51 due to the action of the slant area portion 73 of cam 58 against edge 67a of cutout 67.

During the portion of operation in which solenoid 53 is energized, cam 58 is effective to move away from plate 51 due to the action of surface 73 of that cam' as explained. This motion is effective to engage in cavity 58a post 28a of lever arm 28 in stroking assembly 20. Thus, when solenoid 53 is activated and a force is applied to cam 58a in the direction of that solenoid, a force is also applied by the walls of cavity 58a to arm 28 via post 280. (FIG. 3 shows the distance between lever arm 28 and cam 58 in an exaggerated manner so as to preserve clarity of assembly 20 of that figure. In the present embodiment, the distance is that approximately shown to scale in FIG. 1.)

The action of scissors spring 63 via extension 63a and b on tabs 56a and b respectively are effective during the energized portion of soelenoid 53 so as to maintain a substantially constant force on lever arm 28 of stroking assembly 20 without overloading solenoid 53. The resultant torque applied to arm 16 of assembly 20 is cffective in turn to apply a constant force, for example, 4 pounds to knife blade 12 against honing plate 41. Thus, a calibrated force may be applied to knife 12 against honing plate 41 in response to the selective application of an energizing electrical signal to solenoid FIG. 4shows a diagrammatic view of the glass honing plate 41 and translating honing plate support 42 to getherwith the positioning mechanism for support 42. In that figure, pegs 81a-f are used to position a honing plate 41 with respect to the support 42. Holes 83a-d in the underside of support 42 are used to attach that support via corresponding screws 84a-d mounted in support driver plate 85. In FIG. 4, support 42 is shown in an exaggerated elevated position above plate 85 in order to increase clarity. The vertical position of support 42 and, consequently, honing plate 41 is determined by the position of plate 86, that position being described in detail hereinbelow. Once the position of plate 86 is determined as described below, support 42 is supported by the three lubricated posts 88ac, which posts are in contact with the underside of support 42. In the present embodiment, a rotational lateral translation is provided for support 42 by a motor means 92 which drives gear 91 which in turn drives gears 93 and 194. Support driver plate 85 is attached to offset pins 95 and 96 of gears 93 and 94 in such a manner that plate 85 moves in a circular path having a diameter, for example, of 4 of an inch. As a result, support 42 and plate 41 also move with the same rotary motion'since support 42 is attached to plate 85 via screws 84a-d. Thus, motor 92 is effective to establish a motion of the honing surface of plate 41 in a circular path in the plane of plate 41.

The manner in which the vertical height of plate 41 is established will now be explained in conjunction with FIG. 4. Control 43 on the front'panel of sharpener 10 provides in the present embodiment two selectable positions of plate 86 and, consequently, honing plate 41. Control 43 is connected via a shaft 43a and gears 101 and 102 to shaft 104. Shaft 104 has at the appropriate locations a pair of cams 106 and 107 which rotate in conjunction with shaft 104. The extensions of 104a and b of shaft 104 are anchored in the side walls of sharpener 10. (As shown in FIG. 4, extensions 104a and b are exaggerated in length to provide'a better understanding of that figure. Also, the supporting linkages of shaft 43a are not shown for similar reasons.) Plate 86 is attached via L-brackets 111 and 112 to the four respective triangular plates 116-119. Plates 118 and 119 are not shown in their entirety in the isometric view of FIG. 4. Plates 116-119 are respectively connected with pivoting connections at points 116a-119a to plate L- brackets 111 and 112, shown with exaggerated length in FIG. A second connection to triangular plates 116-119 is made to shafts 121-124 at points 116b-1l9b. The other end of those shafts (shown with exaggerated length in FIG. 3) are connected in a fixed position to the side walls of sharpener 10. Brackets 126 and 127 are connected to plates 116-119 with pivoting connections (shown with exaggerated length in FIG. 4) at points 1160-1190 respectively. Point 119C is not shown in the isometric view of FIG. 4. In the present embodiment, plates 126 and 127 include rectangular cutouts 126a and 127a respectively positioned to surround cams 106 and 107 on shaft 104.

In operation, the 180 rotation of control 43 from the COARSE/LAP POSITION, as shown in FIG. 4, to the FINE POSITION results in the 180 rotation of cams 106 and 107 of shaft 104. As a result of the motion of cams 106 and 107, plates 126 and 127 are driven away from front panel 130 by the action of the cam lobes on the rear edge of cutouts 126a and 127a. As a result, triangular brackets 116-119 are rotated via connections 116c-1 190 about the respective ones of shafts 121-124 in a clockwise direction, as viewed from the left side panel 136. It is understood that shafts 121-124 are in a fixed position and, thus, brackets 116-119 are constrained to rotate about the respective ones of shaft 121-124. As a result, the connection points 116a-119a to brackets 111 and 112 are shifted to a lower position with control 43 in a Fine/LAP position in comparison to that position when control 43 is in the Coarse position. As a result, plate 86 is similarly shifted to a lower position, as are support 42 and honing plate 41. In this manner. the vertical position of the honing surface of plate 41 may be shifted to a new position in response to control 43. The linkage connecting plate 86 with control 43 insures that the two positions allowed for plate 41 are such that the honing surface of that plate lies in one of two parallel planes. In particular, this is achieved by the maintenance of the pivoting points of brackets 116-119 in a fixed position. Since each bracket is rotated through identical angles by plates 126 and 127, the resultant polygons formed by the juncture of points 116a, 1160, 1176 and 117a and points 118a, 1180 and 1196 are congruent parallelograms in each of the two positions of control 43. Further, since the altitudes of congruent parallelograms are equal then, in each of the two positions, the opposite cnds of plate 86 are equidistant from the base of sharpener 10, and thus, plate 86 may lie in one of two parallel planes, depending on the position of control 43. Consequently honing plate 41 also lies in one oftwo parallel planes.

FIG. shows the two-piece removable attachment assembly 140 comprising brace 141 and assembly 150. That assembly is used in the resurfacing of worn honing plates by sharpener 10..In the honing plate resurfacing mode of operation, plate brace 141 is positioned over the support plate 42 and its associated driving assembly. Brace 141 is attached to the side panels of sharpener via thum-screws 142a-145a through holes in tabs 142-145 ofbrace 141 to the appropriately located holes 131-134 in the side panels of sharpener 10 (tab 145 and screw 145a are not shown in the isometric view of FIG. 5). In its attached position, brace 141 is free of any contact with the moving support 42 and glass honing plate 41 which is mounted on support 42.

Brace 141 provides a cutaway portion of its top surface, that cutaway portion being the precise size of a standard type of glass honing plate. The height of the top surface of brace 141 when attached to knife sharpener 10 is such that worn honing plate 41a may be inserted in the cutaway portion in the top surface of brace 141 and that plate is supported by a glass plate 41 on support 42, with support 42 being in its maximum height position (COARSE/LAP, described in conjunction with control 43 above). A pressure assembly is shown in FIG. 5, which assembly may be attached by thumb screws 152 and 153 to brace 141 via holes 147 and 148. When so attached, assembly 150 is effective to apply a substantial downward pressure to an inserted glass honing plate 41a via flexible pads 155 and 156, which pads are attached by coil springs 155a and 156a to assembly 150 at points 158 and 159.

The various modes of operation of sharpener 10 will now be described. The present embodiment of the invention may selectively operate in a one of three modes, as controlled by depressing the appropriate one of switches 45 through 47. Depression of switch 44 is effective to turn sharpener 10 to an OFF state. In a first mode, COARSE (switch 47), a microtome knife may be rapidly sharpened to remove large nicks and scratches. In this mode, the ground edge of the knife will be coarsely ground at a substantially smaller angle to the transverse plane of symmetry of the knife than is desired for a cutting edge. To achieve this angle for the coarsely sharpened facet of the knife, the height of the honing surface of plate 41 is adjusted by a control 43 in the manner described above to the maximum height position, COARSE/LAP. Control 43 on the front panel 130 will be appropriately turned towards COARSE/LAP. After inserting the knife 12 to be sharpened in clamp 14 of stroking assembly 20 and applying an abrasive suspension to the honing surface of plate 41, sharpener 10 operation commences upon depressing COARSE switch 47 on front panel 130. In operation, motor 92 is effective to drive gear 91 which in turn drives gears 93 and 94. The offset pin connections of gears 93 and 94 to plate 85 are effective to drive plate 85 in a circular motion corresponding to the rotation of gears 93 and 94. The linkage of plate 85 to support 42 via the above described screw assemblies through holes 83a-83d is effective to transmit this motion to support 42 which in turn drives honing plate 41 in a corresponding circular path.

Also, upon a depression of switch 47, stroking assembly 20 commences operation. Stroking assembly 20 is effective as described above to repetitively translate in a backward and forward direction along slide rods 22 and 23 at a slow rate, for example, one backward and forward segment every four seconds. As described above, every fourth segment of the backward and forward stroking motion, the knife 12 is flipped to its other side and returned to be in contact with honing plate 41. In this manner, alternate sides of knife 12 are stroked for three full back-and-forth segments while during the forth segment, the knife is flipped and the process repeats for the other side.

In the coarse sharpening mode of operation, solenoid pressure assembly 50 is activated during the three stoking portions of assembly 20 operation. The operation of assembly 50 may be more fully understood by reference to FIG. 3 and the reference set of coordinate axes 49 therein. At such time, when sharpener 10 is not in l the coars sharpening mode and during the every fourth segment of assembly 20 operation when the knife flipping operation occurs, solenoid 53 is not energized and assembly 50 is positioned as shown in FIG. 3. In that figure, solenoid core 53 is in its maximum downward position (negative y-direction as indicated by axes 49) and cam 58 is positioned in its maximum forward position (positive x-direction) so that the striking edge 73 of cam 58 lies within the cutout area 67 of plate 51. Cam 58 is held in this position in part by the force applied by spring 68. During the COARSE mode of operation, in the three stroking cycles of assembly 20, solenoid 53 is energized so that core 53a is positioned in its maximum heightposition (a positive y-direction movement). In response to this change of position, link 55 is effective to move link 56 about screw 61 and, as a result, tab 560 of link 56 applies a force to the extension 63a of spring 63:. The force moment applied to extension 63a of scissors spring 63 is transmitted via extension 63b of spring 63 to tab 57a of link 57. This force applied to tab 57a of link 57 is transmitted from that link to cam 58 in the negative x-direction. The force on cam 58 is effective to drive that earn as guided by screw 58b which moves with respectto the aforedescribed slot in plate 51 (in the negative x-direction).

As surface 73 of cam 58' strikes edge 67a of cutaway 57 of plate 51, cam 58 is driven away from plate 51 (positive z-direction) in addition to the rear (negative x-direction). As cam 58 moves away from plate 51 (positive z-direction) cavity 58a of that cam is positioned so as to surround post 28a of lever arm 28 in stroking assembly 20. Subsequent motion of cam 58 in the reverse direction (negative x-direction) iseffective to apply a force to arm 28 and, consequently, a torque about axis 25 of assembly 20. This resultant torque is applied as described above to the knife 12 in the form of a substantial downward force on that knife against honing plate 41, for example, four pounds. Following the energizing of solenoid 53, the force applied to lever arm 28 is directly responsive and proportional to the spring force of scissors spring 63. In this manner, a consistent force may be applied on subsequent operations without overloading solenoid 53 in the COARSE sharpening mode. Upon achieving a desired coarse edge, sharpener'may be turned OFF by depressing switch 44.

The application of the above described force and the resultant additional pressure applied to knife 12 is effeetive together with the coarse abrasive previously applied to plate 41 to rapidly grind the contact surface of knife 12 with honing plate 41. The addition of this soelnoid generated pressure on knife 12 may enable a time saving in the sharpening of a knife as much as 50 per- I cent compared with sharpening in the absence of this pressure. Although the additional pressure on'knife 12 tends to produce a rapid rate of wearing on plate 41, the rotational motion of that plate, as described above, is effective to distribute the points of wear over a large area of that plate so that the net effect allows the honing plate to wear at a slower rate than in similar microtome knife sharpeners in theprior art. In addition, in the present embodiment, the rotational motion of honing plate 41 is performed at a frequency independent of the cylical stroking of assembly 20. Thereby, successive sharpening operations are performed wherein substantially different contact points are made with plate 41, thus, further distributing the points of wear over the surface area of plate 41. The circular movement of plate 41, together with the stroking of knife 12 by assembly 20, also provides a motion which tends to continuallydistribute the abrasive suspension on plate 41 rather than slide such suspension off to a particular side as is done by machines in the prior art.

In a second mode of operation of sharpener 10, FINE (switch 46), the fine sharpening of the edge of knife 12 is performed. To accomplish this mode of sharpening, a facet must be ground in knife 12, that facet being at a substantially larger angle to the transverse plane of symmetry of knife 12 as compared with the facet ground in the COARSE sharpening mode. A fine abrasive solution is applied to plate 41. Control 43 is adl5 justed to the FINE position, as shown in FIG. 3, so that the resultant motion of the honing surface of plate 41 is toits maximum downward position, as described pre viously.

To sharpen knife 12 as held in clamp 14 in the FINE mode of operation, a fine abrasive suspension is first applied to the honing surface of plate 41. Control 43 is operative to lower the honing surface to the appropriate position as described above. Upon depression of FINE switch 46, the operation of the support 42 assembly begins in an identical fashion to that described in conjunction with the COARSE mode of operation (i.e., support 42 is moved in a circular path), except that in this mode of operation, solenoid pressure assembly 50 is not activated and cam 58 does not engage post 28a. In this manner, the stroking is performed without the additional pressure as generated by solenoid 53, and the only downward force on knife 12 is the resultant from the gravitational force on clamp assembly 14 and on knife 12 itself. Thereby, the FINE sharpening operation is performed at a slower rate than the coarse sharpening. Upon achieving a desired cutting facet, switch 44 may be depressed to terminate operation of sharpener 10.

In the third LAP mode of operation of sharpener 10, (switch 45), two worn honing plates may be resurfaced to provide a uniform honing surface on each by implementing the removable attachment assembly 140. In this mode of operation, no knife is sharpened and, thus, stroking assembly 20 is disabled.

In operation, brace 141 is screwed into position over support assembly 42 via the holes l3l134 and tabs 142-145, as described above. Also, control 43 is positioned to the COARSE/LAP position as shown in FIG. 3 so as to raise support 42 to its maximum height as described above. Following the above specified positioning of control 43, abrasive suspension is applied to plate 41, after which a second plate 41a is inserted in the cutout top surface of brace 141 in a manner such that plate 41a just fits in the cutout area and is supported by the abrasive coated top surface of plate 41. Pressure assembly is then attached via thumbscrews 152 and 153 to brace 141 as described above. As a result of these operations, the bottom surface of the plate 41a and the top surface of plate 41, which are presumably worn in this description, are in contact with each other separated only by the applied abrasive suspension. Furthenassembly 150 is effective via spring loaded pads 155 and 156 to apply a substantial downward pressure on plate 41a against plate 41.

To commence the resurfacing operation, LAP switch 45 is depressed. In response thereto, the support 42 is translated in its circular motion as produced in response to the operation of motor 92, as described above. As a result, plate 41 is translated in the corresponding circular path with respect to the plate 41a which is held stationary by brace 41. The pressure applied by assembly 50, together with the abrasive suspension between brace 4la and 41, is effective to cause a mutual wearing of the worn faces of those plates. In this manner, a resultant uniform honing surface may be produced on the two adjacent surfaces automatically using the same sharpener which is used to sharpen microtome knives. Thus, a single device with a substantially simple attachment may be used as both a knife sharpener and honing plate resurfacing apparatus.

In each of the three above described modes, control 48 may be used as a timer to determine the duration of the sharpener 10 operation. In the present embodiment, control 48 may be set to enable sharpener 10 to operate for any duration between one minute and 45 minutes. Also, in this embodiment, control 48 is effective to terminate operation of sharpener 10 at the first segment of the stroking cycle during which knife 12 is raised from plate 41 which follows the expiration of the time period set by control 48.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

1. Automatic knife sharpening apparatus comprising:

a planar glass honing plate;

a honing plate positioning means to support said honing plate, said honing plate positioning means being selectively operative to position said honing plate in a one of two positions, each of said positions for maintaining the honing surface of said honing plate in a one of two parallel planes;

stroking means for alternately stroking in a straight line a first and second side of a microtome knife against said honing plate positioned by said positioning means, said knife being positioned by said stroking means at a corresponding one of two predetermined angles to said plate; and

a pressure means for selectively applying a substantial pressure to said knife against said honing plate including a solenoid activated forcing means for selectively generating a substantial mechanical force, and a scissors spring force transfer means for transferring said selectively generated force to said stroking means for applying substantial pressure to said knife against said honing plate.

2. An automatic knife sharpening apparatus as defined in claim 1 wherein said first planar glass honing plate is coated with an abrasive suspension.

3. An automatic knife sharpening apparatus as defined in claim 1 wherein said honing plate positioning means further includes a means means for repetitively translating said plate in a circular path in the principal plane of said plate.

4. An automatic knife sharpening apparatus as defined in claim 3 wherein the frequency of repetitive translation of said means for supporting said honing plate is independent of the frequency of said stroking means.

5. An improved apparatus for automatically sharpening microtome knives including an automatic microtome knife sharpening means having an abrasivecoated planar glass honing plate and a stroking means for alternately stroking in a straight line a first and second side of a microtome knife against said honing plate, said knife being positioned by said stroking means at a predetermined angle to said plate, said improvement comprising a translating honing plate support means for supporting and translating said honing plate, said support repetitively translating said plate in a circular path in the principal plane of said plate, the frequency of said repetitive translation being independent of the frequency of repetitive stroking;

a solenoid activated forcing means for selectively generating a substantial mechanical force;

a scissors spring force transfer means for transferring said selectively generated force to said stroking means for applying substantial pressure to said knife against said honing plate; and

a support positioning means for selectively positioning said honing plate support means in a one of a plurality of positions, each of said positions for supporting said honing plate in a one of a plurality of parallel planes, said knife being positioned by said stroking means at a corresponding one of a plurality of predetermined angles to said plate. 

1. Automatic knife sharpening apparatus comprising: a planar glass honing plate; a honing plate positioning means to support said honing plate, said honing plate positioning means being selectively operative to position said honing plate in a one of two positions, each of said positions for maintaining the honing surface of said honing plate in a one of two parallel planes; stroking means for alternately stroking in a straight line a first and second side of a microtome knife against said honing plate positioned by said positioning means, said knife being positioned by said stroking means at a corresponding one of two predetermined angles to said plate; and a pressure means for selectively applying a substantial pressure to said knife against said honing plate including a solenoid activated forcing means for selectively generating a substantial mechanical force, and a scissors spring force transfer means for transferring said selectively generated force to said stroking means for applying substantial pressure to said knife against said honing plate.
 2. An automatic knife sharpening apparatus as defined In claim 1 wherein said first planar glass honing plate is coated with an abrasive suspension.
 3. An automatic knife sharpening apparatus as defined in claim 1 wherein said honing plate positioning means further includes a means means for repetitively translating said plate in a circular path in the principal plane of said plate.
 4. An automatic knife sharpening apparatus as defined in claim 3 wherein the frequency of repetitive translation of said means for supporting said honing plate is independent of the frequency of said stroking means.
 5. An improved apparatus for automatically sharpening microtome knives including an automatic microtome knife sharpening means having an abrasive-coated planar glass honing plate and a stroking means for alternately stroking in a straight line a first and second side of a microtome knife against said honing plate, said knife being positioned by said stroking means at a predetermined angle to said plate, said improvement comprising a translating honing plate support means for supporting and translating said honing plate, said support repetitively translating said plate in a circular path in the principal plane of said plate, the frequency of said repetitive translation being independent of the frequency of repetitive stroking; a solenoid activated forcing means for selectively generating a substantial mechanical force; a scissors spring force transfer means for transferring said selectively generated force to said stroking means for applying substantial pressure to said knife against said honing plate; and a support positioning means for selectively positioning said honing plate support means in a one of a plurality of positions, each of said positions for supporting said honing plate in a one of a plurality of parallel planes, said knife being positioned by said stroking means at a corresponding one of a plurality of predetermined angles to said plate. 